Imaging NFAT-TKGFP reporter system activity with PET and optical fluorescence, plus assessments in tissue samples. (a) Photographic image of a typical mouse bearing different subcutaneous infiltrates (middle panel). Transaxial PET images (GE Advance tomography) of TKGFP expression in a mouse treated with control antibody (left panel) or anti–CD3/CD28 antibodies (right panel) were obtained at the levels indicated by the dashed lines. (b) [¹²⁴I]FIAU accumulation (percent dose/g) in tissue samples of the Jurkat/dcmNFATtgn transduced infiltrates produced from clone 3 and 4 cell lines, wild-type Jurkat infiltrates, and blood plasma, obtained after PET imaging. (c) FACS profiles of TKGFP and CD69 expression in a tissue sample from the same Jurkat/dcmNFATtgn clone 4 infiltrate that was imaged with PET. (d–f) Images of TKGFP fluorescence in a subcutaneous Jurkat/dcmNFATtgn (clone 4) infiltrate were obtained in the same animal (d), first before (e) and then after (f) treatment with anti–CD3/CD28 antibodies. Figure adapted with permission from ref. 26.